1. Field of the Invention
The present invention generally relates to a copying apparatus provided with an automatic light exposure control system for controlling exposure of a light source adapted to apply light to an original document to be copied, and more particularly, to the improvement of the automatic light exposure control system.
2. Description of the Prior Art
In the conventional copying apparatus, the density of an original document is detected for the purpose of obtaining light exposure corresponding thereto. To this end, the conventional copying apparatus generally has an automatic exposure control function for automatically controlling the amount of light applied to the document so that the copying operation may be executed with proper light exposure.
This kind of copying apparatus is provided with a light exposure setting means for setting constant the relationship between the light exposure to be applied to a photoreceptor or photosensitive member and an output of a document density detecting means for detecting the density of the document. Accordingly, proper exposure is automatically applied to each document.
However, in the conventional copying apparatus having the above described automatic exposure control function, an output from a light receiving sensor varies according to the copying apparatus accommodating the senor. This is caused by the characteristic of the sensor, and the position of the sensor in each copying apparatus or the like, even though the amount of light emitted from the light source is rendered to be constant. Accordingly, in the case where the amount of light is automatically controlled, the output for controlling it varies according to the copying apparatus, thus resulting in that the image density of a half-tone document varies with the copying apparatus.